Prime Minister David Cameron faced heavy criticism Thursday for saying a "swarm of migrants" was trying to come to Britain as authorities in France struggle to stop them crossing the Channel.

Prime Minister David Cameron faced heavy criticism Thursday for saying a "swarm of migrants" was trying to come to Britain as authorities in France struggle to stop them crossing the Channel.

"This is very testing, I accept that, because you have got a swarm of people coming across the Mediterranean, seeking a better life, wanting to come to Britain because Britain has got jobs, it's got a growing economy, it's an incredible place to live," Cameron told ITV television during a visit to Vietnam.

Around 3,000 people from countries including Syria and Eritrea are camping out in the northern French port of Calais and trying to cross into Britain illegally by clambering on board lorries and trains.

The controversy has flared up to dominate British media this week as holidaymakers and truck drivers are blocked on the British side due to delays caused by the migrants' actions.

Acting leader of the main opposition Labour party Harriet Harman said Cameron should "remember he is talking about people, not insects".

The Refugee Council, a leading charity which works with asylum seekers, said it was "awful, dehumanising language from a world leader".

And Nigel Farage, leader of the UK Independence Party (UKIP), which wants strict controls on immigration, said he would not use similar words.

"The prime minister is this morning trying to sound tough. Whether he actually means it or not is quite a separate question," Farage told BBC radio.

Cameron is facing calls from tabloid newspapers to deploy the British army to resolve the situation but insists the correct way to tackle it is by working alongside the authorities in France.

"We need to protect our borders by working hand in glove with our neighbours the French and that is exactly what we are doing," he told ITV.

Home Secretary Theresa May on Wednesday chaired a meeting of the government's emergency committee COBRA and the government has pledged £7 million (10 million euros, $11 million) to improve fencing around the Eurotunnel rail terminal at Coquelles, northern France.